Magnetic head

ABSTRACT

A magnetic head having a sliding surface ( 120 ) on which a magnetic recording medium is slid, a magnetic gap g formed in the sliding surface for exchanging information signals with the magnetic recording medium, a track width controlling portion for prescribing a track width Tw of the magnetic gap g, with the track width controlling portion being formed by abutting a pair of magnetic core halves ( 110   a,    110   b ) together, there being track width controlling grooves ( 111   a  to  111   d ) formed in each of the magnetic core halves, metal magnetic films ( 112   a  to  112   f ) provided in association with the magnetic gap g and with the track width controlling portion, and a groove ( 130 ) formed in at least one end of the magnetic gap g for extending substantially parallel to the sliding direction of the magnetic recording medium. A length L in μm between a first point of intersection P between the track width controlling groove ( 111   b ) formed in one of the magnetic core halves ( 110   a ) and one lateral edge of the groove (130) and a second point of intersection Q between the magnetic gap g and the other lateral edge of the groove is related with an intensity of the recording current I [mA] by L≧11.3×1nI−21.9. With the magnetic head, demagnetization produced in the recording track of the magnetic tape is prevented from being produced.

TECHNICAL FIELD

[0001] This invention relates to a magnetic head used for recordingand/or reproducing information signals, such as audio or video signals,for a magnetic recording medium, such as a magnetic tape, or datasignals, handled in an information processing unit, such as a personalcomputer.

BACKGROUND ART

[0002] Up to now, a metal-in-gap (MIG) type magnetic head has been usedas a magnetic head for exchanging the information with a magneticrecording medium, such as a magnetic tape.

[0003] The MIG type magnetic head is formed by abutting and bonding apair of magnetic core halves, formed of ferrites, to each other. Withthis magnetic head, a magnetic gap is formed on abutment surfaces of thepaired magnetic core halves abutted and bonded to each other. Two trackwidth controlling grooves are formed in each of the paired magnetic corehalves forming the magnetic head. These track width controlling groovescontrol the track width of the magnetic gap when the paired magneticcore halves are abutted and bonded together to form the magnetic gap. Inthe MIG type magnetic head, a magnetic metal film is formed in themagnetic gap and in the track width controlling grooves.

[0004] Towards one side, for example an overwrite side, of the magneticgap of the MIG type magnetic head, lying towards a recording trackpreviously formed by sequentially recording information signals on themagnetic tape, there is formed a groove extending parallel to the taperunning direction. This groove is provided for preventing the so-calledside erasure from occurrence. This side erasure is caused by theunneeded stray magnetic flux from being produced from a track edgecorresponding to one end of the magnetic gap to disturb the pattern ofthe recording track recorded on the magnetic tape.

[0005] Referring to FIG. 1, a magnetic head, formed by abutting andbonding a pair of magnetic core halves to each other, is prepared byabutting a first magnetic core half 10 and a second magnetic core half20 to form a head block 1, by applying preset machining operations tothis head block 1 and by slicing the head block 1 into plural discretemagnetic heads.

[0006]FIG. 1 shows the head block 1 obtained on abutting the two paired,that is first and second magnetic core half blocks 10 and 20, and onmachining the resulting product. The head block 1, shown in FIG. 1, isformed by abutting and bonding the first and second magnetic core halfblocks 10 and 20, and is shown in a state prior to severing the blockinto discrete plural magnetic heads. FIG. 1 shows the head block, yet tobe severed into discrete plural magnetic heads, looking from the tapesliding surface formed on each discrete magnetic head.

[0007] In the head block 1, formed on abutting the first and secondmagnetic core half blocks 10 and 20 to each other, there is formed asmagnetic gap g in the abutment surface of the first and second magneticcore half blocks 10 and 20, as shown in FIG. 1.

[0008] In the first magnetic core half block 10, forming the head block1, there are formed a first track width controlling groove 11 and asecond track width controlling groove 12 for controlling the track widthof the magnetic gap g. In the second magnetic core half block 20, thereare similarly formed a first track width controlling groove 21 and asecond track width controlling groove 22 for delimiting a track width Twof the magnetic gap g along with the first and second track widthcontrolling grooves 11, 12 formed in the first magnetic core half block10.

[0009] The track width Tw of the magnetic gap g, formed in the headblock 1, is controlled to high accuracy by the first and second trackwidth controlling grooves 11, 12 and 21, 22 formed in the first andsecond magnetic core half blocks 10 and 20 abutted and bonded to eachother, respectively. The reason is that the width of the abutmentsurfaces of the first and second magnetic core half blocks 10 and 20delimiting the magnetic gap g is precisely controlled by the first andsecond track width controlling grooves 11, 12 and 21, 22 provided in thefirst and second magnetic core half blocks 10 and 20, respectively.

[0010] The head block 1 is sliced along first and second parallelslicing lines E3, E4 on both sides of the magnetic gap g to sever amagnetic head 50. The surface of the so severed magnetic head 50, inwhich is formed the magnetic gap g, serves as a sliding surface 51 onwhich slides the magnetic tape. The magnetic tape is run in slidingcontact with a sliding area on the sliding surface 51, indicated bydotted lines E1 and E2 extending parallel to each other.

[0011] In the sliding surface 51 of the magnetic head 50, severed fromthe head block 1, there is formed a groove 30 for inhibiting sideerasure. This groove is formed towards one end of the magnetic gap g forextending parallel to the tape running direction. The groove 30 isformed to affect a portion of one end of the magnetic gap g.

[0012] On both sides of the magnetic gap g of the magnetic head 50,severed from the head block 1, and in the first and second track widthcontrolling grooves 11, 12, 21, 22, there are provided metal magneticfilms. These metal magnetic films, provided to the magnetic head 50,form magnetic channels for the magnetic flux emanated from the magnetichead. In the groove 30 is charged e.g., glass.

[0013] With the magnetic head 50, including the groove 30 formed in thetape sliding surface, it is possible to prevent the stray magnetic fluxfrom being emanated from the one end of the magnetic gap g provided withthe groove 30, thereby preventing side erasure otherwise caused by thestray magnetic flux.

[0014] Meanwhile, a tape streamer, as a recording and/or reproducingapparatus for recording and/or reproducing data with the use of amagnetic tape as a recording medium and also with the use of a rotarymagnetic head device, is used for providing backup of data handled in aninformation processing unit, such as a computer. Since this sort of therecording and/or reproducing apparatus handles a large quantity of data,the data transfer rate needs to be raised in order to record and/orreproduce data promptly. For increasing the transfer rate, the frequencyof the recording current needs to be raised. If the frequency of therecording current is increased, the current intensity of the recordingcurrent needs to be increased in order to acquire a recording output ofa predetermined level. That is, the intensity of an optimum current fora recording output differs from one frequency to another.

[0015] For example, if the frequency of the recording current is 28 MHz,the recording current to recording output characteristics, shown in FIG.2A, are demonstrated, with the optimum current value for a recordingoutput being approximately 40 mAp-p. If the frequency of the recordingcurrent is 42 MHz, the recording current to recording outputcharacteristics, shown in FIG. 2B, are demonstrated, with the optimumcurrent value for a recording output being approximately 70 mAp-p and,if the frequency of the recording current is 56 MHz, the recordingcurrent to recording output characteristics as shown in FIG. 2C aredemonstrated, with the optimum current value for a recording outputbeing approximately 80 mAp-p.

[0016] With the magnetic head 50, used here, the depth length of themagnetic gap g is 10 μm.

[0017] That is, for increasing the frequency of the recording currentand for recording data at a high transfer rate with optimum recordingcharacteristics, it is necessary to use a large recording current.

[0018] On the other hand, in the recording and/or reproducing apparatusused for recording data handled in an information processing apparatus,it is a requirement to improve reliability as an apparatus as well asdurability. In order to meet these requirements, the magnetic head usedneeds to be improved in durability. For improving the durability of themagnetic head, it is necessary to improve the abrasion resistance of thesliding surface, adapted for having sliding contact with the magnetictape, and to enlarge the depth length of the magnetic gap g.

[0019] If the depth length of the magnetic gap g of the magnetic head isincreased, the intensity of the recording current needs to be increased.

[0020]FIGS. 3, 4 and 5 show the recording current-recording outputcharacteristics in case the frequency of the recording current is set to28 MHz, 42 MHz and to 56 MHz, respectively, with the depth length of themagnetic gap g being 4 μm and 10 μm, respectively. In FIGS. 3 to 5, therecording current-recording output characteristics for the depth lengthof the magnetic gap g of 4 μm and 10 μm are denoted as D and E,respectively.

[0021] When data is recorded using the recording current with thefrequency of 28 MHz, the magnetic head with the depth length of 4 μmexhibits characteristics shown in FIG. 3D, with the recording outputoptimizing current intensity being approximately 35 mAp-p, while themagnetic head with the depth length of 10 μm shows characteristics shownin FIG. 3E, with the recording output optimizing current intensity beingapproximately 40 mAp-p.

[0022] When data is recorded using the recording current with thefrequency of 42 MHz, the magnetic head with the depth length of 4 μmshows characteristics shown in FIG. 4D, with the recording outputoptimizing current intensity being approximately 35 mAp-p, while themagnetic head with the depth length of 10 μm shows characteristics shownin FIG. 4E, with the recording output optimizing current intensity beingapproximately 70 mAp-p.

[0023] When data is recorded using the recording current with thefrequency of 56 MHz, the magnetic head with the depth length of 4 μmshows characteristics shown in FIG. 5D, with the recording outputoptimizing current intensity being approximately 60 mAp-p, while themagnetic head with the depth length of 10 μm shows characteristics shownin FIG. 5E, with the recording output optimizing current intensity beingapproximately 80 mAp-p.

[0024] If, in the magnetic head, the depth length of the magnetic gap gis increased, the recording output optimizing current intensity isincreased. In particular, when the frequency of the recording current isincreased, the recording output optimizing current intensity isincreased further.

[0025] With the discrete magnetic head 50, severed from the head block1, shown in FIG. 1, the track width controlling groove 22 of the secondmagnetic core half block 20 intersects one lateral edge of the parallelgroove 30 on the left side in FIG. 1 at a first point of intersectionshown in FIG. 1. The metal magnetic film, forming the magnetic path asdescribed above, is deposited in the track width controlling groove 22lying at this first point of intersection F. It is noted that theunneeded stray magnetic flux is produced at and near this first point ofintersection F, with the stray magnetic flux increasing with theintensity of the recording current.

[0026] When the recording track of the magnetic tape, on which theinformation signals have already been recorded in the magnetic gap g,traverses the first point of intersection F and its vicinity,demagnetization is produced under the influence of the stray magneticflux emanated from the first point of intersection F and its vicinity.That is, demagnetization is produced in which the information signalsalready recorded in the recording track in the magnetic gap g arepartially erased under the effect of the stray magnetic flux.

[0027] In particular, with the magnetic head in which the transfer rateof data to be recorded on the magnetic tape is increased or in which thedepth length of the magnetic gap g is increased to improve durability,the intensity of the recording current needs to be increased, asdescribed above. If the intensity of the recording current I isincreased, the stray magnetic flux emanating from the first point ofintersection and its vicinity is also increased. For example, if theintensity of the recording current I exceeds 50 mA, the noise level isincreased due to demagnetization in which the information signalsalready recorded on the magnetic tape are partially erased by the straymagnetic flux emanating from the first point of intersection F and itsvicinity, so that information signals cannot be recorded with optimumrecording characteristics.

DISCLOSURE OF THE INVENTION

[0028] It is therefore an object of the present invention to overcomethe aforementioned problems and to provide a magnetic head by means ofwhich information signals can be recorded with an optimum S/N ratio.

[0029] It is another object of the present invention to provide amagnetic head by means of which the transfer rate of the informationsignals to be recorded is raised to enable efficient recording ofinformation signals.

[0030] It is yet another object of the present invention to provide amagnetic head in which durability may be improved and which can be usedfor prolonged time.

[0031] The present invention provides a magnetic head including asliding surface on which a magnetic recording medium is slid, a magneticgap formed in the sliding surface for exchanging information signalswith the magnetic recording medium, a track width controlling portionfor prescribing a track width of the magnetic gap, the track widthcontrolling portion being formed by abutting a pair of magnetic corehalves, there being a track width controlling groove formed in each ofthe magnetic core halves, a metal magnetic film provided in associationwith the magnetic gap and the track width controlling portion, and agroove formed in at least one end of the magnetic gap for extendingsubstantially parallel to the sliding direction of the magneticrecording medium. A length L in μm between a first point of intersectionbetween the track width controlling groove formed in one of the magneticcore halves and one lateral edge of the groove and a second point ofintersection between the magnetic gap and the other lateral edge of thegroove is related with an intensity of the recording current I [mA] by

L≧11.3×1nL−21.9.

[0032] By setting the length L in μm between a first point ofintersection between the track width controlling groove formed in one ofthe magnetic core halves and one lateral edge of the groove and a secondpoint of intersection between the magnetic gap and the other lateraledge of the groove, that is the distance between the metal films lyingon both sides of the groove, as described above, it is possible toprevent the demagnetization otherwise produced in the recording track ofthe magnetic tape to maintain optimum recording characteristics.

[0033] By setting the intensity of the recording current I of theinformation signals to 100 mA or less, it is possible to suppress theeffect of the recording current on the reproducing magnetic head, eventhough the reproducing magnetic head for reproducing the informationsignals recorded by this recording head is mounted in close proximity tothe recording head. Thus, the magnetic head may be applied withadvantage to a rotary magnetic head device of the type adapted forverifying the state of recording of the recorded signals.

[0034] According to the present invention, the plural substantiallystraight lines, formed on the sliding surface by a plurality of trackwidth controlling grooves formed in one of the magnetic core halves, arearranged non-symmetrically relative to an imaginary line extendingperpendicular to the magnetic gap. With this magnetic head, it ispossible to provide a distance larger than a predetermined value betweenthe point of intersection of the track width controlling groove of atleast one magnetic core half and the side erasure prohibiting groove andthe point of intersection of one end of the magnetic gap g and the sideerasure prohibiting groove to prevent these points of intersection frombeing arranged close to each other.

[0035] Other objects, features and advantages of the present inventionwill become more apparent from reading the embodiments of the presentinvention as shown in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036]FIG. 1 is a plan view of a head block formed for producing aconventional magnetic head, looking from a magnetic tape slidingsurface.

[0037]FIG. 2 is a graph showing the relationship between current valuesof plural recoding currents having different frequencies and recordingoutput characteristics.

[0038]FIG. 3 is a graph showing the relationship between current valuesof the recording current, with the frequency of 28 MHz, and therecording output characteristics, for different depths of the magneticgap.

[0039]FIG. 4 is a graph showing the relationship between current valuesof the recording current, with the frequency of 42 MHz, and therecording output characteristics, for different depths of the magneticgap.

[0040]FIG. 5 is a graph showing the relationship between current valuesof the recording current, with the frequency of 56 MHz, and therecording output characteristics, for different depths of the magneticgap.

[0041]FIG. 6 is a perspective view showing a magnetic head according tothe present invention.

[0042]FIG. 7 is a perspective view of the magnetic head according to thepresent invention, looking from the sliding surface of the magnetictape.

[0043]FIG. 8 is a graph showing the relationship between the intensityof the recording current I [mA] and the values of the distance L (μm)between intersection points P, Q for which the demagnetizationphenomenon of recorded signals of the magnetic tape may be prohibitedfrom occurring.

[0044]FIG. 9 is a graph showing the relationship between the recordingcurrent and the block error rate in case of overwriting.

[0045]FIG. 10 shows a portion of a manufacturing process for forming asliding surface of a magnetic head according to the present invention.

[0046]FIG. 11 is a schematic view showing a portion of a manufacturingprocess for a MIG type magnetic head according to a modification of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0047] A magnetic head according to the present invention is nowexplained with reference to several embodiments of the invention shownin the drawings.

[0048] The magnetic head according to the present invention is used in atape streamer magnetic head device which is a recording and/orreproducing apparatus used for providing backup of data handled in aninformation processing apparatus, such as a computer. In this recordingand/or reproducing apparatus, a plural number of magnetic heads aremounted on a rotary drum, on which the magnetic tape is wound, and themagnetic tape running on the peripheral surface of the rotary drum isbrought into sliding contact with the magnetic head which is run inrotation by being mounted on the rotary drum, thereby recordinginformation signals, such as data, or reproducing the informationsignals recorded on the magnetic tape.

[0049] The tape streamer, for which the magnetic head of the presentinvention is used, is of the so-called read-after-write type, in whichdata recording is made by a recording magnetic head as data alreadyrecorded by the recording magnetic head is reproduced by a reproducingmagnetic head, provided in rear of the recording magnetic head, to checkthe data recording state. In a rotary magnetic head device of the systemdescribed above has one or more recording magnetic heads and one or morereproducing magnetic heads are mounted alternately on the rotary drum.For example, plural recording magnetic heads for recording and pluralreproducing magnetic heads are alternately mounted at equi-angularintervals of, for example, 45°, along the circumference of the rotarydrum.

[0050] The rotary drum has a diameter of 40 mm. The distance betweenmagnetic gaps of the recording magnetic head and the reproducingmagnetic head, mounted at an equiangular interval of 45° on the rotarydrum of the above size is approximately 15.3 mm.

[0051] A magnetic head 100 of the present invention, used in this rotarytype magnetic head device, is designed as a MIG (metal-in-gap) typemagnetic head, as shown in FIG. 6.

[0052] The MIG type magnetic head 100, according to the presentinvention, is formed by abutting and bonding paired first and secondmagnetic core halves 110 a, 110 b, formed of ferrite, to each other.With this magnetic head 100, a magnetic gap g is formed on abutmentsurfaces of the paired first and second magnetic core halves 110 a, 110b, abutted and bonded to each other, with the interposition of a gapmaterial, not shown. An upper surface of the magnetic head in FIG. 6, towhich faces the magnetic gap g, acts as a tape sliding surface 120, onwhich slides the magnetic tape as a magnetic recording medium. Thecenter portion of the tape sliding surface 120, in which is formed themagnetic gap g, is swollen outwards to a substantially arcuate surfacewhich is curved along the tape running direction.

[0053] The magnetic gap g facing the tape sliding surface 120 has apreset track width Tw determining the width of a recording track formedby recording the information signals on the magnetic tape. The trackwidth Tw of the magnetic gap g is controlled by the track withcontrolling grooves, which are provided in the first and second magneticcore halves 110 a, 110 b, which are abutted together to form themagnetic head 100, in a manner which will be explained subsequently.

[0054] Referring to FIG. 7, first to fourth track width controllinggrooves 111 a, 111 b, 111 c and 111 d are formed in the first magnetichalf 110 a and the second magnetic half 110 b abutted to each other toform the magnetic head 100. It is noted that the third track widthcontrolling groove 111 c formed in the second magnetic core half 110 bis shown with a dotted line in FIG. 7 because the groove is formedwithin a trimming groove 130 which will be explained subsequently.

[0055] On the bottom surfaces of the first to fourth track widthcontrolling grooves 111 a, 111 b, 111 c and 111 d, are provided in thefirst and second magnetic core halves 110 a, 110 b, there are depositedmetal magnetic films 112 a, 112 b, 112 c and 112 d, respectively. Thesemetal magnetic films 112 a, 112 b, 112 c and 112 d are deposited byforming films of magnetic metal as by sputtering.

[0056] On the abutment surfaces of the first and second magnetic corehalves 110 a, 110 b, abutted to each other to form the magnetic gap g,there are provided metal magnetic films 112 e, 112 f. These metalmagnetic films 112 e, 112 f are formed by forming films of magneticmetal, such as by sputtering, simultaneously with the magnetic metalfilms 112 a to 112 d provided in the first to fourth track widthcontrolling grooves 111 a to 111 d.

[0057] The metal magnetic films 112 e, 112 f are formed on the abutmentsurfaces delimiting the magnetic gap g, so that, more correctly, thetrack width Tw of the magnetic gap g is defined by the metal magneticfilms 112 e, 112 f formed in the abutment surfaces and by the magneticmetal films 112 a to 112 d provided in the first to fourth track widthcontrolling grooves 111 a to 111 d.

[0058] The magnetic metal films 112 a to 112 d provided in the first tofourth track width controlling grooves 111 a to 111 d and the metalmagnetic films 112 e, 112 f provided on the abutment surfaces of thefirst to fourth track width controlling grooves 111 a to 111 d are e.g.,metal magnetic films of high magnetic permeability, formed of aferromagnetic metal material, and form a magnetic path along thelongitudinal direction of the MIG magnetic head 100 of the presentinvention, as shown in FIG. 6, to record information signals on amagnetic tape or to reproduce the information signals recorded on themagnetic tape.

[0059] In the tape sliding surface 120, in which the magnetic gap g isopened, and in which the track width Tw is delimited by the magneticmetal films 112 a to 112, providing the magnetic path, there is formed atrimming groove 130, operating as a pre-mentioned prohibiting groove, asshown in FIG. 7. The trimming groove 130 is formed substantiallyparallel to the direction indicated by arrow X₁ in FIG. 7 correspondingto the running direction of the magnetic tape which is run in slidingcontact with the tape sliding surface 120. This trimming groove 130 isformed at one end of the magnetic gap g, for example, on the overwriteside towards the recording track, on which the information signals havebeen recorded ahead of the magnetic tape, as shown in FIG. 7.

[0060] Since the trimming groove 130 is formed on the information signaloverwrite side, it is possible to prevent unneeded stray magnetic fluxfrom emanating from the track edge of the magnetic gap g in such amanner as to prevent side erasure which tends to disturb the recordingpattern of the recording track formed by recording the informationsignals on the magnetic tape. With the magnetic head 100 of the presentinvention, a point of intersection P between the metal magnetic film 112b and the trimming groove 130 is formed, as shown in FIG. 7.

[0061] On the other hand, a point of intersection Q between the metalmagnetic film 112 e extending substantially parallel to the magnetic gapg of the first magnetic core half 110 a and the trimming groove 130 isformed, as shown in FIG. 7.

[0062] In the magnetic head 100 according to the present invention,stray magnetic flux is generated at the point of intersection P betweenthe metal magnetic film 112 b provided in the track width controllinggroove 111 b and the trimming groove 130. It is necessary to inhibitthis stray magnetic flux to lower the effect on the recording track inwhich the information signals have already been recorded.

[0063] The present inventors have found that, by controlling thedistance L between the point of intersection P between the metalmagnetic film 112 b and the trimming groove 130 and the point ofintersection Q between the metal magnetic film 112 e and the trimminggroove 130, depending on the intensity of the recording current Isupplied to the magnetic head 100, it is possible to inhibit the effectof the stray magnetic flux generated at the point of intersection P.

[0064] That is, by controlling the distance between the points ofintersection P, Q depending on the intensity of the recording current,the phenomenon of demagnetization, in which the pre-recorded signals onthe magnetic tape are partially erased by the unneeded stray magneticflux emanating from the metal magnetic film 112 b at the point ofintersection P, in case information signals are recorded on the magnetictape with the magnetic head 100 according to the present invention.

[0065] The present inventors have found the distance L (μm) for whichthe phenomenon of demagnetization of the pre-recorded signals on themagnetic tape by the unneeded stray magnetic flux emanated from themetal magnetic film 112 b can be inhibited when the recording current I,that is the current 40 mAp-p, 50 map-p, 75 mAp-p and 150 mAp-p, issupplied to the magnetic head 100. Specifically, when the recordingcurrent I is 40 mAp-p, 50 mAp-p, 75 mAp-p and 150 mAp-p, the values ofthe distance L (μm) between the point of intersection P and the point ofintersection Q are 19.5 μm, 22.3 μm, 26.8 μm and 34 μm, respectively.The relationship between the intensity of this recording current I [mA]and the distance L (μm) between the points of intersection P and Q, forwhich the phenomenon of demagnetization of the pre-recorded signals onthe magnetic tape can be inhibited, is shown in FIG. 8.

[0066] It should be noted that the distance L (μm) between the points ofintersection P and Q, for which the phenomenon of demagnetization of thepre-recorded signals on the magnetic tape can be inhibited, isdetermined by the intensity of the recording current I (mA) supplied,and is not affected by the frequency of the recording current I [mA]used.

[0067] From the relationship between the intensity of the recordingcurrent I [mA] and the distance L (μm) between the points ofintersection P and Q, for which the phenomenon of demagnetization of thepre-recorded signals on the magnetic tape can be inhibited, thefollowing relationship:

L≧11.3×1nI−21.9

[0068] is derived.

[0069] An experiment was conducted for finding an error rate of errorsper a preset unit number of bits, for example, 256 bits, when datahandled on a computer using the magnetic head 100 is overwritten on themagnetic tape. The results of the experiment are shown in FIG. 9. Thedata overwrite on the magnetic tape means overwrite recording on data,already recorded on the magnetic tape prior to overwriting, withoutperforming an independent erasure operation. The error rate means theprobability that the data recorded on the magnetic tape prior to dataoverwrite is not completely erased but is left over. As shown in FIG. 9,the block error rate is optimum for the recording current I of 50 mAp-pand, when the recording current I is approximately 30 to 100 mAp-p, theblock error rate may be reduced such that data can be recorded as anoptimum S/N is maintained.

[0070] With the magnetic head 100 according to the present invention,the transfer rate of the information signals to be recorded may beraised, such that the information signals can be recorded efficiently.Thus, the magnetic head of the present invention can be used withadvantage for a recording and/or reproducing apparatus employing therecording current of a high intensity, such as 50 to 100 mAp-p, for ahigher frequency.

[0071] With the magnetic head 100 according to the present invention,the block error rate can be lowered and data can be recorded at anoptimum S/N ratio, when the recording current is approximately 50 to 100mAp-p, so that, even when the magnetic head of the present invention isapplied to a recording and/or reproducing apparatus of the pre-mentionedread-after-write system, the data stored on the recording magnetic headcan be read out accurately by the reproducing magnetic head withoutaffecting the reproducing magnetic head. In particular, when themagnetic head is applied to a rotary magnetic head device in whichrecording magnetic heads and reproducing magnetic heads are arranged atan equiangular distance of 45° on a rotary drum 40 mm in diameter, withthe distance between the magnetic gaps g being approximately 15.3 mm, itis possible to inhibit the effect the recording magnetic head has on thereproducing magnetic head to enable the data recorded by the recordingmagnetic head to be read out correctly by the reproducing magnetic head.

[0072] Meanwhile, in the conventional MIG magnetic head, a track widthcontrolling groove 21 and a track width controlling groove 22 of thefirst magnetic core half block 20, corresponding to the first magneticcore half 110 a of the MIG magnetic head 100 of the present invention,are arranged symmetrically with respect to an imaginary line Iperpendicular to the magnetic gap g, as shown in FIG. 1 alreadyexplained.

[0073] That is, the track width controlling groove 21 and the trackwidth controlling groove 22 are formed at an angle θ₁ and at an angle ofθ₂, respectively, with respect to a parallel line to the imaginary lineI, with the angles θ₁ and θ₂ both being e.g., 30°. Since the track widthcontrolling groove 22 is formed in this manner, the contact pointbetween the metal magnetic film formed in the track width controllinggroove 22 and the parallel groove 30 is a point of intersection F, asshown in FIG. 1.

[0074] On the other hand, the contact point between the metal magneticfilm of the magnetic core half block 20 of the magnetic gap g and theparallel groove 30 is a point of intersection H, as shown in FIG. 1. Thelength between the points of intersection F and H is appreciably shorterthan the length between the points of intersection P and Q of the MIGmagnetic head 100 of the present invention. The result is thatpre-mentioned phenomenon of demagnetization by the unneeded straymagnetic field, generated in the metal magnetic film, is produced at thepoint of intersection F of FIG. 1, thus erasing a portion of the signalspre-recorded on the magnetic tape.

[0075] With the MIG magnetic head 100 according to the presentinvention, the phenomenon of demagnetization, such as is produced in theconventional magnetic head, in which part of the pre-recorded signals onthe magnetic tape are erased, is not produced and can be suppressedeffectively.

[0076] With the magnetic head 100 according to the present invention,the track width controlling groove 111 b of the first magnetic core half110 a is formed at an angle of approximately 90° relative to a lineparallel to the magnetic gap g, as shown in FIG. 7. Thus, when the metalmagnetic film 112 b is formed on the track width controlling groove11lb, such as by sputtering, the metal magnetic film 112 b can bethinner than other portions, and hence the metal magnetic film 112 b canbe thinner at the pre-mentioned point of intersection P in FIG. 7 thanother portions. Thus, it is possible to reduce the unneeded straymagnetic field at the point of intersection P to inhibit the phenomenonof demagnetization more effectively.

[0077] The hatched portions of FIGS. 6 and 7 are charged with anon-magnetic material, such as glass, while the trimming groove 130 isalso charged with the nonmagnetic material, such as glass.

[0078]FIG. 10 shows a portion of the manufacturing process for formingthe tape sliding surface 120 shown in FIG. 7.

[0079]FIG. 10 shows the state prior to separation into plural magneticheads shown in FIG. 7. More specifically, first and second magnetic corehalves 210 a, 210 b are abutted to each other to form a block of pluralmagnetic heads. This block can be severed into plural MIG magnetic heads100 by slicing along cutting lines, not shown, lying outside dottedlines shown in FIG. 10, with the dotted line being an abutment widthprocessing line prescribing the area of sliding contact with themagnetic tape. Since the first and second magnetic core halves 210 a,210 b are each comprised of a side-by-side repetition of the samestructures, only a portion of each of the magnetic core halves ishereinafter explained.

[0080] Referring to FIG. 10, in a portion of the magnetic core halvesforming a sole MIG magnetic head 100, the abutting portions of the firstmagnetic core half block 210 a and the second magnetic core half block210 b form the magnetic gap g with a metal magnetic film, not shown,in-between. The track width controlling grooves 111 a, 111 b are formedin the first magnetic core half block 210 a. The track width controllinggroove 111 a is formed at an angle θ, for example, at an angle of 30°,as described above, relative to a line parallel to the imaginary line I,as shown in FIG. 10. The track width controlling groove 111 b isarranged at approximately 90° with respect to the magnetic gap g. Thatis, the track width controlling groove 111 a and so forth are arrangednon-symmetrically relative to the imaginary line I. The track widthcontrolling grooves 111 c, 111 d are formed in a manner similar to themanner in which the track width controlling grooves 111 a, 111 b areformed. The state of FIG. 10 is achieved by abutting the magnetic corehalf blocks to each other, using the second magnetic core half block 210b.

[0081] Meanwhile, the trimming groove 130 is formed in each magnetic gapg of FIG. 10. Thus, by abutting the magnetic core halves,non-symmetrical with respect to the imaginary line I, to each other, thedistance between the points of intersection P and Q may be elongated toenable the production of the MIG magnetic head 100 unsusceptible to thephenomenon of demagnetization.

[0082] The magnetic head 100 according to the present invention may beformed through the manufacturing process shown in FIG. 11.

[0083] Meanwhile, since FIG. 11 has many structural portions in commonwith FIG. 10, common structural portions are depicted by the samereference numerals and are not explained, while only the points ofdifference are mainly explained.

[0084] In FIG. 11, the track width controlling grooves 111 a, 111 b ofthe first magnetic core half block 210 a shown on the lower side in FIG.11 and the track width controlling grooves 311 d, 311 c of the secondmagnetic core half block 310 b shown on the upper side in FIG. 11 aredifferent, and hence the magnetic core half blocks are non-symmetrical.

[0085] In this configuration, the length between the points ofintersection P and Q may be elongated. As a consequence, not only thephenomenon of demagnetization in which the information signalspreviously recorded on the magnetic tape are erased may be preventedfrom occurrence, but also the angle of the track width controllinggrooves 311 d, 311 c on the upper side in the drawing unrelated with thephenomenon of demagnetization may be selectively set as more importanceis attached to magnetic head characteristics.

[0086] For example, only the track width controlling groove 111 b of thefirst magnetic core half block 210 a is set to an angle of approximately90° relative to the magnetic gap g, as shown in FIG. 11, while the angleθ of each of the remaining track width controlling grooves 111 a, 311 c,31ld may be set to the same value of, for example, 3020 .

[0087] The present invention is not limited to the above-describedembodiment, but may be optionally modified without changing its purport.

Industrial Applicability

[0088] With the present invention, described above, a magnetic head maybe provided in which the recording current is increased and the transferrate of the information signals to be recorded is raised to enable theinformation signals to be recorded efficiently. Moreover, the magnetichead is improved in durability and usable for prolonged time.

1. A magnetic head comprising a sliding surface on which a magneticrecording medium is slid, a magnetic gap formed in said sliding surfacefor exchanging information signals with said magnetic recording medium,a track width controlling portion for prescribing a track width of saidmagnetic gap, said track width controlling portion being formed byabutting a pair of magnetic core halves, there being a track widthcontrolling groove formed in each of said magnetic core halves, a metalmagnetic film provided in association with said magnetic gap and saidtrack width controlling portion, and a groove formed in at least one endof said magnetic gap for extending substantially parallel to the slidingdirection of said magnetic recording medium, wherein a length L in μmbetween a first point of intersection between said track widthcontrolling groove formed in one of said magnetic core halves and onelateral edge of said groove and a second point of intersection betweensaid magnetic gap and the other lateral edge of said groove is relatedwith an intensity of the recording current I [mA] by L≧11.3×1nI−21.9. 2.The magnetic head according to claim 1 wherein the recording currentintensity I is 50 to 100 mAp-p.
 3. The magnetic head according to claim1 wherein a plurality of substantially straight lines formed on saidsliding surface, by a plurality of said track width controlling groovesformed in one of said magnetic core halves, are arrangednon-symmetrically relative to an imaginary line extending perpendicularto said magnetic gap.